package controlGraph;

/**
 * Polymorphic structure.
 * @author Petey
 *
 */
public abstract class Expression {
	public abstract String toString();
	
	
	//No use
	public boolean isSame(Expression e){
		System.out.println("isSame() of abstract class is called");
		System.exit(1);
		return false;
	}
}
